Respostas

2013-08-17T21:38:40-03:00
A) x+y= 11
x=11-y

x-y=3
(11-y)-y=3
11-2y=3
-2y=3-11
-2y=-8
y=4

x=11-y
x=11-4
x=7

B)x+y=6
x=6-y

2x+y=4
2(6-y)+y=4
12-2y+y=4
-y=4-12
-y=-8
y=8

x=6-y
x=6-8
x=-2

C)x-y=6
x=y+6

x+y=-7
(y+6)+y=-7
2y+6=-7
2y=-7-6
2y=-13
y=-6,5

x=y+6
x=-6,5+6
x=-0,5

D)2x+y=4
2(5-3y)+y=4 <- (substitui o x por 5-3y)
10-6y+y=4
-5y=4-10
-5y=-6
y=6/5 ou y=1,2

x=5-3(1,2)
x=5-3,6
x=1,4
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